Enhanced Mechanical Properties of Al2O3 Nanoceramics via Low Temperature Spark Plasma Sintering of Amorphous Powders

In this work, Al2O3 nanoceramics were prepared by spark plasma sintering of amorphous powders and polycrystalline powders with similar particle sizes. Effective comparisons of sintering processes and ultimate products depending on starting powder conditions were explored. To ensure near-full density higher than 98% of the Al2O3 nanoceramics, the threshold temperature in SPS is 1450 degrees C for polycrystalline Al2O3 powders and 1300 degrees C for amorphous powders. The low SPS temperature for amorphous powders is attributed to the metastable state with high free energy of amorphous powders. The Al2O3 nanoceramics prepared by amorphous powders display a mean grain size of 170 nm, and superior mechanical properties, including high bending strength of 870 MPa, Vickers hardness of 20.5 GPa and fracture toughness of 4.3 MPa.m(1/2). Furthermore, the Al2O3 nanoceramics prepared by amorphous powders showed a larger dynamic strength and dynamic strain. The toughening mechanism with predominant transgranular fracture is explained based on the separation of quasi-boundaries.

Automated summary

In this study, Al2O3 nanoceramics were synthesized through spark plasma sintering (SPS) of amorphous and polycrystalline powders with similar particle sizes. The sintering processes and resulting products were compared based on the starting powder conditions. The threshold temperature for achieving near-full density of the Al2O3 nanoceramics was found to be 1450°C for polycrystalline powders and 1300°C for amorphous powders. The nanoceramics prepared from amorphous powders exhibited a mean grain size of 170 nm and superior mechanical properties, including high bending strength, Vickers hardness, and fracture toughness. Additionally, they showed larger dynamic strength and dynamic strain compared to those prepared from polycrystalline powders. The toughening mechanism was explained based on the separation of quasi-boundaries.